The isolation of a new,low-potential,iron-containing electron-transfer protein from rumen bacteria

A new low-potential iron-containing electron-transfer protein has been isolated from cell free extracts of rumen bacteria. This protein, like some bacterial ferredoxins, can 1) transfer electrons from illuminated spinach chloroplasts to NADP; 2) catalyze ferredoxin dependent reductive carboxylation reactions; 3) act as electron acceptor in the pyruvate lyase catalyzed reaction in which pyruvate is oxidized to acetyl-CoA and CO₂. Unlike ferredoxin, this low potential iron protein contains no acid-labile sulfide; contains tightly bound iron that is released only after prolonged hydrolysis with 6 N HCl at 105°C and with an optical spectrum different from that associated with the bacterial ferredoxins.